The invention concerns a rubber bushing that suppresses vibrations hydraulically. The bushing, which is preponderantly subjected to loads perpendicular to its axis, comprises two axially coincident supporting sleeves arranged one inside the other and a rubber resilient element retained between the sleeves. The resilient element forms at least two essentially radially projecting webs having metal contact elements on the outer surfaces that rest against the inner surface of the outer supporting sleeve. The webs demarcate, in conjunction with the walls at each end of the sleeve and with the outer supporting sleeve, at least two working chambers that are full of fluid and communicate with each other through connecting channels. The webs are resiliently compressed to less than their nominal size between the two retaining supporting sleeves. The ends of the webs are outwardly secured in the vicinity of the walls to mechanical rings demarcating, in conjunction with the outer supporting sleeve, annular channels that constitute part of the connecting channels. The annular channels, extending around each end of the resilient element, terminate at and conduct fluid into a working chamber inside the element.
A bushing of this type is known from German patent publication No. OS 3 724 432. Its advantage is that, when it is subjected to load, the compressed webs prevent any significant tension in the resilient element. It is also possible to vary its suppression capacity by varying the geometrical dimensions of the annular channel at each end of the bushing. A long and slender channel, for example, is appropriate for suppressing low-frequency vibrations and two separate and parallel channels are appropriate for suppressing high-frequency vibrations.
The geometry of the fluid-conducting channels and hence the bushing's suppression curve cannot, however, be varied once the component has been installed and is in operation. Although some separate vibration frequencies can be suppressed with different embodiments of the known bushing, suppression of a wide range of frequencies is not possible. A lot of different-size bushings must accordingly be kept in stock, which is troublesome and expensive. Another drawback occurs when, for example, an extremely loosely mounted engine vibrates with a frequency as low as approximately 5 Hz. In such an event, the attainable rate of suppression is severely limited by the length of the annular channels around the bushing's circumference.